The purpose of this project is the study of genome structure and function of the Aleutian disease of mink parvovirus (ADV). Approximately 85% of the DNA sequence of the attenuated ADV-G strain has been deduced using the M13-based dideoxy methods. The findings suggest that the overall organization is similar to that of other nondefective parvoviurses, but that homology at both the nucleotide and predicted protein level is less than 50%. Molecular clones representing the 15-88 map units (MU) were derived directly from two in vivo passaged virulent ADV strains and compared to ADV-G. Detailed restriction mapping indicated that the viruses were very closely related and that the segments of all three viruses were the same size. Clones of all three expressed antigens in E. coli that reacted with sera specific for virion, capsid proteins, but, in spite of the fact that the DNA segments are identical in length, the proteins encoded by clones of the two in vivo viruses were 2-3 kd larger than those of ADV-G. This finding may be important because the capsid proteins found in particles from virulent viruses also are 2-3 kd larger than the comparable ADV-G capsid proteins. DNA sequence comparison between these two viruses and ADV-G is underway.